fdo#79530 Update help for minimum length of password

Since some time, password only required 1 character (as indicated in UI)
instead of 5 as indicated in help

Change-Id: Id7fef69ee273ee622365b4077d83cd46368475c6
Reviewed-on: https://gerrit.libreoffice.org/9624
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>